In this expert opinion statement, Professor Richard James, Emeritus Professor of Microbiology, University of Nottingham Medical School, considers the microbiological risks presented by inhalation and direct skin contact with surgical smoke
CSJ has recently been campaigning to raise awareness of the potential risks posed by smoke plumes in operating theatres and has canvassed staff about their concerns, through interviews and reader surveys. In this expert opinion statement, Professor Richard James, Emeritus Professor of Microbiology, University of Nottingham Medical School will focus on the evidence for the microbiological risks presented by inhalation and direct skin contact with surgical smoke and discusses what measures can protect healthcare staff against these risks
What is surgical smoke?
Tools to achieve haemostasis and dissection include electrosurgery units and lasers. Electrosurgery units use high-frequency current to cut and coagulate tissue, which releases the cellular fluid as steam that drives the cell contents into the air forming a surgical smoke plume. Lasers produce high temperatures that boil and rupture the tissue cells, releasing steam containing cell contents (Barrett, 2003).1
Surgical smoke has a distinctive odour and can cause symptoms such as watery eyes and sore throat in healthcare staff who are exposed to it. Surgical smoke contains many chemicals, including acrylonitrile and hydrogen cyanide, along with bacteria and viruses. Several reviews of the potential contents of surgical smoke have been published (Bree et al., 2017; Vortman, 2021).2,3 It has been reported that approximately 500,000 healthcare workers, such as surgeons, nurses, anaesthesiologists, and technicians, are exposed to surgical smoke in operating rooms each year, and the damage from smoke exposure accumulates over their careers (Choi et al., 2014).4
The microbiological risks of surgical smoke
Skin and mucosal lesions when treated surgically, using electrosurgery and lasers, generate a surgical smoke plume containing vapourised and burnt tissue. The possibility that surgeons might inhale viral particles such as HPV from surgical smoke, during the removal of certain lesions, was suggested in 1995 (Gloster & Roenigk, 1995).5 The presence of a number of other viruses, or viral nucleic acid, in surgical smoke has been observed; including HIV DNA (Baggish et al., 1991);6 hepatitis B virus (Kwak et al., 2016)7 and human coronavirus RNA (Yokoe et al., 2021).8
The most sensitive method to detect the presence of HPV in a sample is to use a PCR amplification method that detects HPV DNA. Some studies have reported that HPV DNA was not found in surgical smoke and that the risk of HPV infection was low for healthcare workers (Weyandt, 2011; Manson, 2013).9,10 Many other studies have demonstrated the presence of HPV DNA in surgical smoke (Sood, 1994; Zhou, 2019; Hu, 2021).11,12,13 A study from Germany reported the presence of HPV DNA in surgical smoke during LEEP, and the subtype of HPV in the smoke was consistent with that in the patients being operated upon (Neumann, 2018).14
The presence of viral nucleic acid, in surgical smoke plumes, by itself, is not direct evidence of a microbiological risk to surgeons who are exposed to it. Since HPV transmission can also occur via other routes, such as contact with HPV-contaminated gloves after surgery, or during sexual contacts, identification of the source of an HPV infection can be challenging.
A recent review identified only three case reports describing HPV-associated upper airway disease due to exposure to surgical smoke (Palma, 2021).15 The first report involved a 44-year-old surgeon, who had treated rectal lesions using a laser over the course of three years, who developed laryngeal papillomatosis associated with HPV subtypes 6 and 11. He had used a surgical mask, gloves, and eye protection, but no specific smoke evacuation system (Hallmo, 1991).16
The second report concerned a 28-year-old gynaecology nurse, who had regularly assisted in electrocautery and laser treatments of anogenital condylomata without proper protective equipment, and developed laryngeal papillomatosis. After extensive evaluation by a virology institute, this case was legally accepted in Germany as an occupational disease based upon suspected airborne HPV transmission (Calero, 2003).17 The third report involved two gynaecologists (Rioux, 2013).18 Patient A was in a long-term monogamous relationship with his wife and denied any other sexual contacts. His wife was tested after patient A’s diagnosis and was HPV negative. Patient B was married twice.
A large study of 700 gynaecologists in 67 local hospitals in China who have performed electrosurgery, including the loop electrosurgery excision procedure (LEEP), investigated if they are at risk of acquiring HPV DNA through surgical smoke (Hu, 2021).13
The findings demonstrated that the HPV infection rate in the nasal epithelial cells of the gynaecologists who performed LEEP was 10.11%, which was significantly higher than the 2.91% observed in the gynaecologists who did not perform LEEP. The most prevalent HPV genotype was HPV16, which was found in 76.19% of the electrosurgery group. Follow up studies of the gynaecologists who had HPV positive nasal swabs showed that 43.48% returned a negative result after 3 months, and 100% became negative after 24 months.
The authors of this study concluded that the nasal HPV infection was transient in the gynaecologists studied, and that LEEP may cause inactivation of the HPV DNA in surgical smoke and thus prevent it from resulting in HPV-associated disease.
In this regard, it is of interest that a recent systematic review (Fox-Lewis, 2020)19 concluded that:
- Surgical smoke from the treatment of HPV-related lesions can contain HPV DNA, and that this can contaminate the upper airways of operating theatre staff;
- It is not known whether surgical smoke contains inactivated viral DNA or viable HPV capable of infecting those it comes into contact with;
- An increased prevalence of HPV infection or HPV-related disease in Operating Theatre staff following occupational exposure to surgical smoke has not been convincingly shown.
A recent meta-analysis showed that operating room personnel who participated in ablation procedures, such as laser irradiation, LEEP and cryosurgery, were at risk for HPV transmission (Palma, 2021).15 The authors stated that longitudinal studies, including baseline HPV status and the objective evaluation of HPV associated lesions in medical staff, with and without ablation smoke exposure, are needed to estimate the risk and confirm causality
A systematic review (RobertsonMoore, 2021)20 identified the risk of viral transmission in surgical smoke, with HPV as the only virus that demonstrated clinical infection in humans exposed to surgical smoke. Human immunodeficiency virus, hepatitis B virus and varicella zoster virus tended not to be transmissible.
How to protect staff from surgical smoke
Even before the risks of exposure to surgical smoke were appreciated, a randomised clinical trial revealed that suction clearance of the diathermy smoke plume resulted in a significant reduction in the amount of smoke reaching the level of the operator’s mask (Pillinger, 2003).21
A review into the dangers of electrosurgical smoke to operating room personnel (Bree, 2017)2 concluded that:
- Inadequate steps are being taken to protect operating room personnel from the harmful effects of surgical smoke, which contains particulate matter, various chemicals, and some microorganisms.
- Standard surgical masks are ineffective at filtering potentially harmful substances from electrosurgical smoke; N95 respirators are the preferred personal protective equipment for operating room personnel exposed to harmful chemicals during electrosurgery.
- Smoke evacuation systems or suction devices should be used whenever electrosurgery is performed and should be no further than 2 inches from the source of the smoke.
A comprehensive review of the protective measures that could be taken to protect gynaecologists from surgical smoke (Liu, 2019)22, indicated that:
- Masks such as N95 are important but not sufficient to provide respiratory protection for wearers.
- General room ventilation using a central system connected to several operating rooms was insufficient to effectively capture smoke generated at the surgical site.
- Another important precaution is proper and diligent use of a smoke evacuation system with a high efficiency filter.
A review suggested that suitable precautionary measures for surgical smoke include: appropriate masks and eyewear, smoke evacuation, ventilation and suction (Searle, 2020).23 This review also stated that surgical masks confer little protection to the respiratory tract against aerosols generated during surgery or CO2 laser procedures. To reduce the quantity of smoke plume generated, operators should consider using bipolar (as opposed to unipolar or monopolar) cautery at the lowest power settings. Mechanisms to remove the generated plumes through vacuum extraction should be implemented, as well as the use of appropriate personal protective equipment.
A review of occupational reproductive hazards for female surgeons in operating rooms (Anderson, 2020)24 reported that a survey of 1,021 US female surgeons across different specialties found an overall pregnancy complication rate of 35.3%, compared with 14.5% in the general population. No studies specifically examining the effects of surgical smoke on reproductive outcomes have been carried out, despite the knowledge that several components of surgical smoke are reproductive toxins, and that exposure to fine particulate matter from air pollution has been associated with low birth weight and pre-term labour. Based on their review of the evidence, the authors recommend that priority should be given to controlling exposure to surgical smoke by the following measures:
- Install and maintain an operating room ventilation system.
- Mandate use of smoke evacuators with adequate capture velocity.
- Use smoke evacuator systems during laparoscopic surgery.
- Consider use of high filtration masks for standard surgical procedures and N95 respirators for aerosol-generating procedures.
The British Association of Dermatologists Position Statement (BAD, 2021)25 reviewed the evidence of the risk to surgeons from infectious agents in surgical smoke and stated that “Risk of surgical plume to patients, assistants and surgeons can be reduced if the plume is removed by means of a smoke extractor used during surgery. These are relatively low-cost portable devices that can be used when surgeons consider that there may be risk.”
The BAD Position Statement calls for:
- Smoke extractors to be available in all settings where dermatology surgery takes place, so that surgeons can use these devices when they consider it appropriate.
- Further occupational health research into the risks of virus in surgical plume.
A systematic review and meta-analysis indicates that simple safety measures greatly reduce HPV contamination and transmission risk (Palma, 2021).15 These include the use, but also correct disposal, of examination gloves, aprons, caps and appropriate (regularly cleaned or disposable) eye protection. Closely positioned local smoke exhaustion systems and highly efficient filters, as well as appropriate room ventilation, are central to virus transmission control along with adherence to established HPV related hygiene guidelines. Fortunately, the use of N95 masks and, to some extent, even surgical masks were shown to effectively reduce contamination of nasal epithelia with HPV DNA.
The precautions needed to minimise the risk of HPV transmission from surgical smoke suggested in the systematic review (Robertson-More, 2021)20 include the use of smoke evacuation systems with a HEPA or ULPA filter, and through the proper use of recommended personal protective equipment including diligence in donning/ doffing techniques
In addition to adopting many of the measures suggested by the Resumption of laser/IPL skin services post COVID-19 lockdown — British Medical Laser Association (BMLA) guidance document for laser devices, including use of personal protective equipment and smoke evacuation devices, it was suggested (Searle, 2021)26 that practitioners using electrocautery in their clinics may also wish to consider the use of bipolar (rather than unipolar) devices and lower energy settings when using electrocautery devices, both of which are associated with reduced generation of plumes.
Significant aerosol concentrations were observed during all aerosol-generating procedures with concentrations exceeding 3×106 particles per 100 ml (Schramm, 2021).27 Considerable reductions in concentrations were observed with mitigation. The greatest reduction (97.38 to>99.9%) was observed when combining irrigation and filtration. Coagulating diathermy reduced concentrations by 88.0–96.6% relative to cutting but produced larger particles. Suction alone, and suction with filtration, reduced aerosol concentration by 41.0–49.6% and 88.9–97.4% respectively. No tested mitigation strategies returned aerosol concentrations to baseline.
A recent paper concluded that maskwearing (alone) during laser procedures is ineffective for preventing contamination, and that a smoke/plume evacuator is the most effective way to reduce viral contamination (Stetkovich, 2021).28 The authors also recommend using a smoke evacuator within two inches of the site of the HPV lesions being treated with laser therapy.
A recent cohort study of 75,011 female nurses with 15 or more years of employment in Operating Rooms revealed a 69% greater risk of developing chronic obstructive pulmonary disease compared to those who never worked in an Operating Room (Xie, 2021).29
A recent review described the measures required to reduce the risk from surgical smoke as minimising the generation, managing the smoke aerosol and barrier methods to prevent inhalation (Hill, 2021).30 The review concludes that “Guidance on surgical diathermy smoke extractor use should be implemented in a standardised way to protect healthcare workers.”
Finally, a very recent review states that approximately 500,000 healthcare workers are exposed to surgical smoke in operating rooms each year and that damage from smoke exposure accumulates over their careers (Yan, 2022).31 The authors concluded that surgical smoke is an occupational hazard to both healthcare workers and that high-filtration surgical masks and smoke evacuation systems are necessary for protection. Many of these precautions have not been implemented due to their cost, noise, resistance from doctors, lack of repair equipment or replacement parts, and large local exhaust ventilator devices.
Surgical smoke regulation
The current HSE Guidance on Diathermy and surgical smoke states that: “Diathermy emissions can contain numerous toxic gases, particles and vapours and are usually invisible to the naked eye. Their inhalation can adversely affect surgeon’s and theatre staff’s respiratory system. The risks vary according to individual circumstances, such as the procedure, equipment, environment technique and patient.”
The Control of Substances Hazardous to Health Regulations require employers to carry out an assessment of the risks from hazardous substances and to always try to prevent exposure at source. If exposure to diathermy emissions can’t be prevented then it should be adequately controlled. This is usually achieved by effective local exhaust ventilation (LEV). Typically this takes the form of extraction incorporated into the electrosurgery system to remove emissions at source, known as ‘on-tip’ extraction.” (HSE).32
The HSE guidance on surgical smoke is derived from an HSE Evidence based literature review (HSE RR922, 2012).33 Its main findings include:
- The limited published data indicate that dedicated smoke evacuation/extraction devices are effective at reducing the levels of surgical smoke during various surgical procedures, when compared to levels when no evacuation system is present.
- The available data originate from a variety of equipment types and surgical specialisations but suggest that correct (close) positioning of smoke evacuation devices to source emissions, if not already tip mounted, is likely to be important to the efficiency of surgical smoke removal.
The more litigious culture in the US, and the activity of staff and members of the Association of Perioperative Registered Nurses, perhaps explain why surgical smoke evacuation legislation was enacted in three US states in 2021 – Kentucky, Oregon and Illinois. In addition, surgical smoke evacuation legislation bills were introduced in Connecticut, Georgia, Iowa, New Jersey, Ohio, Pennsylvania and Texas. In 2022, the Connecticut, Missouri, Utah and Washington state legislatures will consider similar bills (AORN, 2021).34
A recently published article (Frampton, 2022)35 discusses the Guidance and Regulations that have a role in protecting staff from the harmful effects of surgical smoke. A particularly important point made in the article is that the range of staff at potential risk from surgical smoke includes gynaecologists, perioperative practitioners, surgeons, dermatologists, nurses and colposcopists, and that when the surgery is performed in outpatients departments, where there is little or no ventilation, then the risk to these staff is likely to be even greater.
Conclusions:
Microbiological Risks of Surgical Smoke
1. HPV DNA has been detected in surgical smoke in a large number of published studies.
2. Only three case reports describing upper airway disease due to exposure to surgical smoke have been published. One of these cases was legally accepted in Germany as an occupational disease based upon suspected airborne HPV transmission.
3. In contrast to the paucity of case reports supporting HPV transmission among healthcare workers, and the suggestion that LEEP may cause inactivation of HPV DNA in surgical smoke, the surgical smoke plume obtained from laser treatment of mouse tail warts was found to be highly infectious to uninfected nude mice (Best, 2020).36
4. Identification of relevant occupational HPV transmission to healthcare workers from surgical smoke is complicated by there being other potential transmission routes associated with workplace contamination.
5. HPV transmission to healthcare workers may also be associated with the HPV status of their sexual contacts, which could reduce their willingness to report potential cases of HPV occupational disease.
How to protect staff from surgical smoke
1. Many reviews that have examined the microbial risks of surgical smoke in Operating Rooms are in favour of the use of appropriate precautionary measures, which include: a) Masks such as N95. b) General room ventilation. c) The use of a smoke evacuation system with a high efficiency filter, that is located very close to the surgical site.
2.The majority of the reviews of the microbial risks of surgical smoke stress the importance of an effective smoke evacuation system.
3. Recognition of the possibility that there may be occupational reproductive hazards from exposure to surgical smoke for female healthcare workers.
4. The HSE Guidance on surgical smoke makes it clear that dedicated smoke evacuation/extraction devices positioned close to the source are effective at reducing the levels of surgical smoke.
5. The large number of UK healthcare workers exposed to surgical smoke, both in Operating Rooms and Outpatient Departments, indicates that the UK Guidance on the use of a smoke extractor during operations that generate surgical smoke needs to be significantly strengthened.
6. Surgical smoke evacuation legislation is increasingly being enacted, or introduced, in many US States.
* Declaration of interest: The preparation of this article required an extensive review of the literature on surgical smoke by Professor Richard James, which was facilitated by the payment of a consultancy fee by Vernacare Limited. The conclusions on the potential risks of surgical smoke presented in this article were not influenced by this payment.
About the author
Professor Richard James taught key Medical Microbiology topics such as the mechanism of action of antibiotics, antibiotic resistance, and the prevention and control of infections to undergraduate, postgraduate and medical students for over 40 years. He was the Head of the School of Clinical Laboratory Sciences (one of the six schools within the University of Nottingham Medical School) for six years. In 2007 he founded the Centre for Healthcare Associated Infections at The University of Nottingham.
References
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